The present invention relates generally to a copier, and in particular to an electrostatic copier.
The term "electrostatic copier" as used herein is intended to include a xerographic copier. In such electrostatic copiers it is known to place the pattern sheets which are to be copied or produced face down onto a transparent supporting plate or the like, and light is directed against the underside of the transparent plate and a system of mirrors and lens arrangements is used to form a reproduction of the indicia on a copy sheet, either directly or mediately by means of a copy drum.
It is often desirable to be able to copy only portions of a pattern sheet, for example to copy certain lines of indicia on a pattern sheet which should be placed in a desired relationship relative to parts of a form, for example relative to boxes or the like provided as part of a form. It has been proposed in the prior art to provide an arrangement wherein a first set composed of two or more pattern sheets is used having information that is always required on the copy to be made, for example various boxes of a form. The pattern sheets of this first set are stationary and a pattern sheet of a second set is movable relative to the pattern sheet of the first set so that different lines of indicia are provided on the pattern sheet of the second set become exposed in the gap, to be reproduced on a copy sheet together with the information on the pattern sheets of the first set. For example, it is often desirable to provide a work preparation plan which is produced to begin with in its entirety, and of which different portions are to be copied for subsequent use, each portion to contain only parts of the total plan. Thus, parts of the total plan may be used for salary calculating purposes, for material-allocating purposes, for time-allocating purposes, and the like. For these purposes, only those portions of the overall plan which are relevant to the particular copy, need be reproduced. To make copies of this type, copy sheets can be provided on which the necessary basic information is already preprinted, so that only those portions of the overall plan need be copied onto the copy sheets which are relevant to the particular requirement. However, this means that an adequate quantity of preprinted copy sheets be kept available at all times, which is often disadvantageous because the supply may run out just when these preprinted copy sheets are needed most urgently. Also, preprinting of the copy sheets involves additional work and expenses, and if the type of copy to be made changes frequently it requires additional work to replace a supply of one type of preprinted copy sheet with a supply of a different type of preprinted copy sheets.